The present invention relates to a system and method for injecting a working fluid, such as injecting water or a water solution, into hydrocarbon combustion engines and, more specifically, to a fluid injection system and method for injecting fluid into spark-ignition and compression-ignition engines in which the injection rate is proportional to the engine speed and engine exhaust gas pressure.
Various cooling fluids, such as water and water in solution with other substances including hydrocarbon liquids such as methenol, have been commonly injected into hydrocarbon engines, both of the spark-ignition and compression-ignition type, to provide improved engine operation. The fluid absorbs heat within the combustion chamber and provides for an even burning rate to prevent or at least greatly mininize detonation of the fuel charge in the combustion chamber. In addition, the fluid tends to diminish the accumulation of carbon deposits within the combustion chamber and, because the combustion process takes place at a generally lower temperature, inhibits the formation of high-temperature pollutants, specifically the oxides of nitrogen (NO.sub.x).
Various types of prior devices have been used to introduce cooling fluids into the intake air of internal combustion engines, either as a finely divided spray or by increasing the humidity of the intake air. These devices have included nozzle-type injectors and intake air humidifiers which are operated directly by the exhaust gases from the engine or either directly or indirectly in reponse to engine intake manifold pressure or engine speed. While these devices have generally provided some engine performance improvement, they have operated in a manner not totally responsive to engine requirements. Thus, in some prior systems, the fluid injection rate may be adequate under certain engine operating conditions, such as the constant-speed cruise condition, while the injection rate during other engine operating conditions, such as acceleration and deceleration may be too little or too much. When the fluid injection rate is insufficient, the beneficial effects of the cooling fluid are, of course, not obtained. Conversely, when the injection rate is too high the surplus of fluid within the combustion chamber tends to quench the combustion process and, of course, diminish engine performance.